1. Field of the Invention
The invention relates to a device and method for restoring lung function, and more particularly, the invention relates to a device and method for restoring the elasticity or recoil of a lung to improve pulmonary function by increasing gas exchange or for restoring the efficiency of the lung by compressing the less useful, diseased portions of the lungs.
2. Brief Description of the Related Art
Chronic obstructive pulmonary diseases (COPD), such as emphysema are steadily increasing in frequency, possibly due to continued smoking, increasing air pollution, and the continued aging of the population. Emphysema patients have reduced lung capacity and efficiency due to the breakdown of lung tissue often caused by smoking. Healthy lung tissue includes a multitude of air passageways leading to tiny air sacks called alveoli throughout the lung which inflate and deflate with air when we breath. The alveoli are small, tightly packed, polyhedral recesses composed of a fibrillated connective tissue and surrounded by a few involuntary muscular and elastic fibers. The thin walls of the alveoli perform gas exchange as we inhale and exhale. The lungs are expanded to draw air into the alveoli by moving the diaphragm downward and moving the chest outward. The air is expelled from the lungs by the natural elasticity or recoil of the lung tissue in combination with the pushing of the diaphragm back up into place by the abdominal contents.
In the lungs of an emphysema patient, the walls between adjacent alveoli within the alveolar sac deteriorate. This wall deterioration is accelerated by the chemicals in smoke which affect the production of mucus in the lungs. Although the breakdown of the walls of the alveoli in the lungs occurs over time even in a healthy patient, this deterioration is greatly accelerated in a smoker causing the smoker""s lungs to have multiple large spaces with few connecting walls instead of the much smaller and more dense alveoli spaces in healthy lung tissue.
In a diseased emphysematous lung many of the walls of alveoli and other lung tissue are deteriorated. Because of the deterioration, the diseased lung has larger open spaces and a larger overall volume than a healthy lung. However, the diseased lung is less efficient as it has less wall tissue to achieve gas exchange.
In addition, deterioration of the lung tissue in an emphysematous lung reduces the amount of elastic fibers within the lung and thus reduces the overall elasticity of the lung. The reduction of the lung""s elasticity permits the chest wall to pull the lung outward more easily and reduces the lung""s ability to contract or recoil to expel air. This inability of the lung tissue to recoil results in a larger residual volume of air remaining in the lungs after exhalation. Consequently, this increased residual gas volume interferes with the ability of the lung to draw in additional gas during inspiration. As a result, a person with advanced COPD can only take short shallow breaths. Accordingly, emphysema patients often have a flattened diaphragm, a barrel chest or enlarged chest, and shoulders which are shrugged upwards. When patients with severe emphysema take in as much air as their chest cavity can accommodate, they still have insufficient gas exchange because their chest is full of non-functional air filling the large cavities in the lungs. This non-functional residual air cannot be expelled from the lungs. As a result, this decreased lung efficiency causes even the most ordinary activities to be extremely difficult causing the patient to lose mobility.
In cases of severe emphysema, lung volume reduction surgery (LVRS) attempts to improve lung efficiency to allow the patient to regain mobility. In lung volume reduction surgery, a diseased portion of an emphysematous lung having alveolar wall deterioration is surgically removed. LVRS is performed by opening the chest cavity, retracting the ribs, stapling off, and removing the more diseased portion of the lung. The removal of the diseased lung tissue allows the remaining healthier tissue to inflate more fully and take greater advantage of the body""s ability to inhale and exhale. Since there is more air and more gas exchange in the healthier portion of the lung, lung efficiency improves.
LVRS addresses the loss in lung efficiency but does not address the loss of the natural lung tissue elasticity in a diseased lung. In addition, LVRS is an extremely invasive procedure having substantial risks of serious post-operative complications, such as pneumothorax, and requires an extended convalescence.
Accordingly, it is desirable to achieve improved lung efficiency for emphysema patients by improving lung elasticity or recoil, or by providing a means to reduce the volume of the diseased portions of the lung through tissue compression.
The present invention relates to a device and method to improve lung efficiency by restoring recoil of an emphysematous or otherwise unhealthy lung. The present invention may also improve lung efficiency by reducing the volume of diseased portions of the lung through compression of lung. Compressing certain portions of lung tissue prevents expansion and over-inflation of this lung tissue which increases the volume within the chest cavity and allows otherwise increased expansion of relatively healthier lung tissue. A device for either restoring recoil or mechanically compressing lung tissue may include at least one elastic member positioned inside or outside of the lung and which is secured to the lung tissue and supplements the natural elasticity of the lung or compresses that portion of lung.
In accordance with one variation of the present invention, a device for restoring lung recoil ability may include a bio-compatible elastic member having at least a first end and a second end, the elastic member having sufficient elasticity which is capable of compressing lung tissue when applied to a lung. The elastic member may also be capable of being stretched by the lung tissue during inhalation. The first end and the second end of the elastic member may be fixed to the lung tissue with the elastic member in a stretched condition to improve the elasticity of a lung.
The variations describe above may also be configured to have an elasticity which, when placed over a compressed lung or a compressed portion of the lung, prevents expansion of the lung tissue during inspiration. Alternatively, the present invention includes a covering which prevents the lung or portions of the lung from significantly expanding in volume during inspiration. These variations may also be configured to mechanically compress the diseased lung tissue as well.